greenfield



(No Model) E. T. GREENFI'ELD.

ARMORBD ELECTRICAL OONDUIT.

No. 585,863. 7 Patented July 6, 1897.

IRON

DlL-C PAPE WITNESSES INVE/l 7'08 11 TTOIi/IEV i FFQEQ EDWVIN T. GREENFIELD, OF BROOKLYN, NEW YORK, ASSIGNOR TO THE INTERIOR OONDUIT AND INSULATION COMPANY, OF NEIV YORK, N. Y.

ARMORED ELECTRICAL CONDUIT.

SPECIFICATION forming part of Letters Patent No. 585,863, dated July 6, 1897.

Application filed October 7, 1896. Serial No. 608,146. (No model.)

To all whom it may concern.-

Be it known that I, EDWIN T. GREENFIELD, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have made a new and useful Invention in Armored Electrical Conduits, of which the following is a specification.

My invention relates to that class of electrical conduits having a strong external metallic tube or armor and an inner tube or lining of fibrous insulating material, such as is disclosed in United States Patent No. 552,060, granted to me on December 24, 1895.

-I have found in the practical use of ironarmored conduit-tubes in which paper treated with asphalt under heat is used as the insulating material that under certain conditions of temperature and moisture the insulatinglining will become percolated with moisture to such an extent as to deteriorate its insulating capacity; and it was with a view of overcoming this objectionable feature that the present invention was devised.

My invention will be fully understood by referring to the accompanying drawing,which is a longitudinal sectional view of an armored conduit-tube embodying my improvement.

Referring to the drawing in detail, I represents an iron or equivalent metal armor-tube, 0 an interior lining closely adhering to the inner wall thereof, and P an inner insulating tube. This interior lining is composed, preferably, of oil-cloth or any fibrous material which has been thoroughly subjected to a bath of oil or any equivalent substance which renders it impervious to water and is then coated on either or both sides with an oil, paint, or any equivalent substance adapted to cause it to adhere to the armontube.

I prefer to construct my improved armored electrical conduit in the following manner: The inner or insulating tube P is preferably made of paper of any desired thickness by any of the wellknown methods now in general use. I then form around or draw over this tube P a coating or layer 0 of oil-cloth with the painted surface thereof on the out side and unite the same to the tube P by means of paste in a manner well known to those skilled in the art of tube construction. The armor-tube I is then heated to a temperature sufficient to cause the paint to become adhesive, and the tube P, with its coating 0, is forced into it. The compound tube so formed is then subjected to a bath of molten pitch or asphalt in such manner as to entirely impregnate the inner tube P with the molten material. This resultis accomplished, by successive dippings into the molten material in a manner well known by those skilled in the art until the pores of the inner tube are sufficiently filled with the molten material and the armor tube I covered with a coating thereof. The heat of the tube I when the tube P is forced into the same softens the painted outer surface of the coating 0, so that when it coolsit adheres to the inner wall of the armor-tube and secures the inner and outer tubes firmly together.

' I do not limit myself to the use of paper tubes or linings, but claim the use of inner tubes or linings composed of any porous or absorbent insulating material; nor do I limit myself to the method of manufacture above described, as it is evident to the skilled person that it may be varied in several particulars and still result in the production of a conduit having an external metallic armor, an internal tube or lining of insulating material, and an interposed layer of fibrous material which is impervious to moisture, nor do I limit myself to the use of the commercial article of trade known as oil-cloth for the lining next to the inner wall of the armor-tube, as I may use for this lining any fibrous material which has been treated with oil or with any insulating agent impervious to moistureas, for instance, cotton, wool, or other cloth fabric, paper, or, in fact, any fibrous material which can be thoroughly saturated with a moistureresisting agent or I may use in place of the oil-cloth O a lining of any flexible fibrous material treated with rubber, either on one or both surfaces or throughout its meshes or mass, my invention being designed to comprehend generically the use of a lining between the walls of the inner insulating-tube and the iron armor which shall be under ordinary conditions of temperature and usage impervious to moisture and which will readily yield or bend with the armor without rupturing or otherwise impairing the integrity or imperviousness of the moisture resisting agent. This conduit may be bent cold without impairing its insulating and moisture-resisting qualities, which is a highly useful and important function in the work of installing the conduit.

I make no claim in the present application to a conduit-tube composed of a metal armor and an interior lining of oil-cloth with the painted surface adhering to the inner Wall of the armor, nor to a conduit-tube composed of an armor lined with a fibrous material which has been treated with oil or any insulating agent which is impervious to moisture, as

' this subject-matter is claimed in a separate application filed by me in the United States Patent Oflice on the th day of December, 1896, and bearing Serial No. 615,116.

Having thus described my invention, what I claim, and desire to secure by Letters Patent of the United States, is

1. A conduit having an external metallic armor, an internal tube or lining of insulating material,and an interposed layer of fibrous material which is impervious to moisture, substantially as described.

2. A conduit consisting of a metal armor, a lining of insulating material and an intermediate lining of fibrous material treated with oil, substantially as described.

3. A conduit consisting of a metal armor, a lining of insulating material and an intermediate lining of fibrous material treated with oil, said intermediate lining'firmly adhering to the interior wall of the armor and to the lining of insulating material, substantially as described.

4;. Aconduit-tube consisting of a metal armor and a lining of oil-cloth with its painted surface adhering to the inner wall thereof, in combination with an inner lining of insulating material adhering to the inner Wall of the oil-cloth lining, substantially as described.

5. A conduit-tube consisting of a metal armor, a lining of oil-cloth having its painted surface closely adhering to the inner wall of the armor and an interior lining of paper treated with an insulating material, substantially as described.

6. A conduit-tube consisting of an. iron armor, a lining of oil-cloth with the painted surface thereof adhering to the inner Wall of the armor and an interior lining of paper, the whole having been treated with heated asphalt or pitch in such mann eras to thoroughly impregnate the pores of the inner lining and cover the outer surface of the iron armor, substantially as described.

In testimony whereof I have hereunto subscribed my name this 1st day of October, 1896.

EDIVIN T. GREENFIELD.

Witnesses:

ALLAN O. BAKEWELL, CHARLES J. KINTNER. 

